From c8bb99b30e770668675128ddd3fb67e87c9376e1 Mon Sep 17 00:00:00 2001
From: Arun Isaac
Date: Mon, 26 Aug 2019 01:57:22 +0530
Subject: Use grouping functions to handle multiple tags and languages.

* ennu.el (ennu-many-to-many-group-by): New function.
(ennu-publish): Use grouping functions seq-group-by and
ennu-many-to-many-group-by instead of seq-filter to handle multiple
tags and languages.
---
 ennu.el | 48 +++++++++++++++++++++++++++++-------------------
 1 file changed, 29 insertions(+), 19 deletions(-)

diff --git a/ennu.el b/ennu.el
index 76a2dbe..7169b9a 100644
--- a/ennu.el
+++ b/ennu.el
@@ -365,6 +365,22 @@ value of the last form in BODY."
      (unwind-protect ,@body
        (delete-directory ,temporary-directory t))))
 
+(defun ennu-many-to-many-group-by (function sequence)
+  "Apply FUNCTION to each element of SEQUENCE.
+Separate the elements of SEQUENCE into an alist using the results
+as keys. Keys are compared using `equal'."
+  (seq-reduce
+   (lambda (result element)
+     (seq-do
+      (lambda (key)
+        (map-put result key
+                 (cons element (map-elt result key nil 'equal))
+                 'equal))
+      (funcall function element))
+     result)
+   (seq-reverse sequence)
+   nil))
+
 (defun ennu-publish ()
   (interactive)
   (let ((make-backup-files nil)
@@ -375,9 +391,7 @@ value of the last form in BODY."
         (seq-do
          (apply-partially 'ennu--do-operation temporary-directory)
          (append
-          (let* ((posts (ennu-posts (ennu-setting :posts-directory)))
-                 (tags (seq-uniq (seq-mapcat 'ennu-post-tags posts)))
-                 (tongues (seq-uniq (seq-map 'ennu-post-tongue posts))))
+          (let ((posts (ennu-posts (ennu-setting :posts-directory))))
             (append
              ;; Publish posts
              (seq-map 'ennu-publish-post posts)
@@ -388,22 +402,18 @@ value of the last form in BODY."
                                       (seq-take posts (ennu-setting :atom-feed-number-of-posts))))
              ;; Publish indices
              (seq-map
-              (lambda (tongue)
-                (ennu-publish-index
-                 "index" tongue blog-title posts-per-page
-                 (seq-filter (lambda (post)
-                               (string= tongue (ennu-post-tongue post)))
-                             posts)))
-              tongues)
-             (seq-map
-              (lambda (tag)
-                (let ((posts (seq-filter (lambda (post)
-                                           (member tag (ennu-post-tags post)))
-                                         posts)))
-                  (ennu-publish-index
-                   (ennu--expand-relative tag (ennu-setting :tag-directory))
-                   (ennu-post-tongue (first posts)) tag "" posts-per-page posts)))
-              tags)
+              (pcase-lambda (`(,tongue . ,posts))
+                (ennu-publish-index "index" tongue blog-title posts-per-page posts))
+              (seq-group-by 'ennu-post-tongue posts))
+             (seq-mapcat
+              (pcase-lambda (`(,tag . ,posts))
+                (seq-map
+                 (pcase-lambda (`(,tongue . ,posts))
+                   (ennu-publish-index
+                    (ennu--expand-relative tag (ennu-setting :tag-directory))
+                    tongue tag posts-per-page posts))
+                 (seq-group-by 'ennu-post-tongue posts)))
+              (ennu-many-to-many-group-by 'ennu-post-tags posts))
              ;; Publish links
              (seq-map 'ennu-publish-link
                       (seq-uniq (seq-mapcat 'ennu-post-links posts)))
-- 
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